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Monday, 9 January 2012

Mullaperiyar Dam Safety

Saftey

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After the 1979 Morvi Dam failure which killed up to 25,000 people, safety concerns of the aging Mullaperiyar dam's and alleged leaks and cracks in the structure were raised by the Kerala Government. A Kerala government institution, Centre for Earth Science Studies (CESS), Thiruvananthapuram, had reported that the structure would not withstand an earthquake above magnitude 6 on the Richter scale. The dam was also inspected by the Chairman, CWC (Central Water Commission). On the orders of the CWC, the Tamil Nadu government lowered the storage level from 142.2 feet to 136 feet, conducted safety repairs and strengthened the dam.
Strengthening measures adopted by Tamil Nadu PWD from 1979 onwards include cable anchoring of the dam's structure and RCC backing for the front slope. During a recent scanning of the Mullaperiyar dam using a remotely operated vehicle by the Central Soil and Materials Research Station on directions from the Empowered Committee of the Supreme Court, the Kerala Government observer opined that "mistakes in the strengthening works carried out by Tamil Nadu" in 1979 damaged the masonry of the dam.
Current safety concerns hinge around several issues. Since the dam was constructed using stone ruble masonry with lime mortar grouting following prevailing 19th century construction techniques that have now become archaic, seepage and leaks from the dam have caused concern. Moreover, the dam is situated in a seismically active zone. An earthquake measuring 4.5 on the Richter scale occurred on June 7, 1988 with maximum damage in Nedumkandam and Kallar (within 20 km of the dam). Consequently several earthquake tremors have occurred in the area in recent times. These could be reservoir-induced seismicity, requiring further studies according to experts. A report by IIT Roorkee states that the dam "was likely to face damage if an earthquake of the magnitude of 6.5 on the Richter scale struck its vicinity when the water level is at 136 feet".

For Tamil Nadu, the Mullaperiyar dam and the diverted Periyar waters act as a lifeline for Theni, Madurai, Sivaganga and Ramnad districts, providing water for irrigation and drinking, and also for generation of power in Lower Periyar Power Station. Tamil Nadu has insisted on exercising its unfettered rights to control the dam and its waters, based on the 1866 lease agreement. Kerala has pointed out the unfairness in the 1886 lease agreement and has challenged its validity. However, safety concerns posed by the 116-year old dam to the safety of the people of Kerala in the event of a dam collapse, have been the focus of disputes from 2009 onwards. Kerala's proposal for decommissioning the dam and constructing a new one has been challenged by Tamil Nadu.
Tamil Nadu has insisted on raising the water level in the dam to 142 feet, pointing out crop failures. One estimate states that "the crop losses to Tamil Nadu, because of the reduction in the height of the dam, between 1980 and 2005 is a whopping 40,000 crores. In the process the farmers of the erstwhile rain shadow areas in Tamil Nadu who had started a thrice yearly cropping pattern had to go back to the bi-annual cropping."

Construction of new Dam

Kerala enacted the Kerala Irrigation and Water Conservation (Amendment) Act, 2006 to ensure safety of all 'endangered' dams in the State, listed in the second schedule to the Act. Section 62A of the Act provides for listing in the schedule, "details of the dams which are endangered on account of their age, degeneration, degradation, structural or other impediments as are specified". The second schedule to the Act lists Mullaperiyar (dam) constructed in 1895 and fixes 136 feet as its maximum water level. The Act empowers Kerala Dam Safety Authority (Authority specified in the Act) to oversee safety of dams in the State and sec 62(e) empowers the Authority to direct the custodian (of a dam) "to suspend the functioning of any dam, to decommission any dam or restrict the functioning of any dam if public safety or threat to human life or property, so require". The Authority can conduct periodical inspection of any dam listed in the schedule.
In pursuance of Kerala's dam safety law declaring Mullaperiyar dam as an endangered dam, in September 2009, the Ministry of Environment and Forests of Government of India granted environmental clearance to Kerala for conducting survey for new dam downstream. Tamil Nadu approached Supreme Court for a stay order against the clearance; however, the plea was rejected. Consequently, the survey was started in October, 2009. On Sept. 9, 2009 stated it had already communicated to the Government of India as well as to the Government of Kerala that there is no need for construction of a new dam by the Kerala Government, as the existing dam after it is strengthened, functions like a new dam.